A linear accelerator (Linac) is a particle accelerator that uses an electromagnetic field to accelerate charged particles to high speeds. The principle is to use the force of an electric field to act on charged particles, causing them to be accelerated. Then, guided by the electromagnetic field, they accelerate along a straight path, ultimately reaching the desired specific velocity.

A linear accelerator mainly consists of four parts: an acceleration chamber, a driver, a power supply, and a modulator. The acceleration chamber is a device for accelerating charged particles, and the driver is a device that generates high-frequency electromagnetic fields. The power supply provides energy to the driver, and the modulator adjusts the time and intensity of energy output to control the speed of acceleration and the time structure of the particle beam.




In a linear accelerator, charged particles are placed in the acceleration chamber, which can generate high-frequency electromagnetic fields, causing the particles to be accelerated. When a particle enters the acceleration chamber, the electromagnetic field accelerates the particle to a high velocity and then causes it to continue accelerating along a straight line until it reaches the desired velocity. There is a set of periodic electric and magnetic fields inside the acceleration chamber, which interact with each other to drive charged particles. When charged particles pass through an accelerating cavity, they interact with the electric and magnetic fields, thus being accelerated to higher speeds.

The driver is a key component that generates high-frequency electromagnetic fields, which interact with particles to generate acceleration. The generation of electromagnetic fields is usually achieved through the use of radio frequency (RF) power sources. Radio frequency waves pass through a series of structures that form an accelerating cavity, forming a high-frequency electromagnetic field within it. This electromagnetic field alternates repeatedly in the accelerating cavity, which is the high-frequency field. Then the charged particles pass through the high-frequency electromagnetic field in the accelerating cavity and are accelerated to higher speeds.

The power supply is the device that supplies energy to the drive and is responsible for providing the required energy. In a linear accelerator, the energy input of the power supply must match the design speed and structure of the accelerator. Usually, the emitting electrode (gun) inputs a simple constant current to generate an initial acceleration of increasing speed. Then, the radio frequency energy is added to the structure of the acceleration cavity. For example, when an accelerator needs to reach 1MeV, it needs a 1MeV power supply and it needs to transfer electrical energy to the RF driver.

A modulator is an energy regulating device used to adjust radio frequency power to control the time structure of a particle beam. The modulator will modify the RF energy output in the power supply to generate the required energy waveform, ensuring that the electromagnetic field is transmitted normally to the acceleration chamber at various specific time sequences. Modulators typically use simple electronic devices such as transistors, diodes, and capacitors, which can frequently change current and voltage to produce the desired time waveform.

In summary, a linear accelerator is a device that uses electromagnetic fields to accelerate charged particles to high speeds. Its main components include an acceleration chamber, driver, power supply, and modulator. When charged particles enter the acceleration chamber, the electromagnetic field accelerates them to a higher speed until the desired speed is reached. Linear accelerators are widely used in fields such as medicine, physics, and industrial research, and play a crucial role in scientific and technological progress.